Tunable ground planes in plasma chambers

ABSTRACT

An apparatus and method are provided for controlling the intensity and distribution of a plasma discharge in a plasma chamber. In one embodiment, a shaped electrode is embedded in a substrate support to provide an electric field with radial and axial components inside the chamber. In another embodiment, the face plate electrode of the showerhead assembly is divided into zones by isolators, enabling different voltages to be applied to the different zones. Additionally, one or more electrodes may be embedded in the chamber side walls.

BACKGROUND

1. Field

Embodiments of the present invention generally relate to an apparatusand method for depositing or removing materials on a substrate. Moreparticularly, embodiments of the present invention relate to anapparatus and method for controlling the intensity and/or distributionof a plasma discharge in a plasma chamber.

2. Description of the Related Art

Plasma enhanced processes, such as plasma enhanced chemical vapordeposition (PECVD) processes, high density plasma chemical vapordeposition (HDPCVD) processes, plasma immersion ion implantationprocesses, and plasma etch processes, have become common processes usedin depositing materials on substrates and/or removing materials from asubstrate to form structures.

Plasma provides many advantages in manufacturing semiconductor devices.For example, using plasma enables a wide range of applications due tolowered processing temperature, enhanced gap-fill for high aspect ratiogaps, and higher deposition rates.

A challenge that is present in conventional plasma processing systems isthe control of the plasma to attain uniform etching and deposition. Akey factor in the etch rate and deposition uniformity is the spatialdistribution of the plasma during processing. For example, in aconventional PECVD chamber, which are typically parallel plate reactors,the traditional factors affecting the spatial distribution of the plasmaare chamber pressure, distance between electrodes, and chemistry, amongother factors. While conventional control of plasma distribution inPECVD chambers produces satisfactory results, the process may beimproved. One challenge that remains in plasma processing isnon-uniformity or uneven deposition of bulk material, such as conductivematerials, dielectric materials, or semiconductive materials, to form athin film on the substrate.

FIG. 1A (prior art) is a cross-sectional view of a substrate 1illustrating one challenge caused, at least in part, by non-uniformityin conventional plasma chambers. The substrate 1 includes a plurality ofstructures 5, which may be trenches, vias, and the like, formed therein.A layer 10 of conductive, dielectric, or semiconductive material formedthereon by a conventional plasma process substantially covers thesubstrate 1 and fills the structures 5. The substrate 1 has a dimensionD₁, which may be a length or width in the case of a rectangularsubstrate, or an outside diameter in the case of a round substrate. Inthis example, substrate 1 is a round substrate and dimension D₁ is anoutside diameter, which may be equal to about 300 mm or 200 mm.

As stated above, the layer 10 substantially covers the substrate 1 buteffectively stops at a dimension D₂, which leaves a peripheral portionof the substrate 1 having little or no material thereon. In one example,if dimension D₁ is 300 mm, dimension D₂ may be about 298 mm, whichproduces about a 1 mm portion around the periphery of the substrate 1having little or no material thereon, which reduces device yield on thesubstrate 1 as the periphery of the substrate 1 is effectively unusable.Such defects are sometimes referred to as edge effects or plasma edgeeffects.

FIG. 1B (prior art) is an exploded cross-sectional view of substrate 1of FIG. 1A showing a surface area 20 on the periphery of the substrate 1illustrating another challenge caused, at least in part, bynon-uniformity in conventional plasma chambers. The edge region 25 isshown uncovered due to the device yield reduction described above. Inaddition, conventional plasma processes may produce region 15 along theperiphery of the substrate, which may be an area where excessivedeposition and build-up of material occurs. In subsequent processes,substrate 1 may undergo a chemical mechanical polishing (CMP) process orother planarization or polishing process to remove a portion of layer10. In the subsequent process, region 15 may create challenges sinceregion 15 must be removed along with layer 10. As region 15 may includea height D₃ of between a few hundred angstroms (A) to thousands of Aabove surface area 20 of layer 10, throughput may be negatively impactedin the subsequent process. Additionally, removal of region 15 may causeoverpolishing of surface area 20, which may result in damage to devicesor structures formed on substrate 1.

Therefore, there is a need for an apparatus and method to provideenhanced control of the spatial distribution of plasma in a plasmachamber to address the challenges described above.

SUMMARY OF THE INVENTION

Embodiments described herein generally provide methods and apparatus forcontrolling the spatial distribution of a plasma in a plasma chamberusing a secondary ground plane.

One embodiment provides an apparatus for processing a substrate,comprising a substrate support; one or more electrodes coupled to thesubstrate support; a showerhead assembly having a face plate opposingthe substrate support; and one or more ground elements spaced radiallyaway from the substrate support, wherein the substrate support and theface plate cooperatively define a processing volume and the one or moreelectrodes are adapted to generate a tunable electric field inside theprocessing volume having axial and radial components.

Another embodiment provides an apparatus for supporting a substrate in aprocessing chamber, comprising a support surface; a thermal controlelement disposed within the support surface; an electrode disposedwithin the support surface, wherein the electrode has a first portiondefining a first plane and a second portion defining an angled surface,and the angled surface intersects the first plane; and a tuner coupledto the electrode.

Another embodiment provides a method of controlling the spatialdistribution of a capacitively coupled plasma, comprising positioning afirst electrode inside a processing chamber, positioning a first groundplane inside the processing chamber and facing the first electrode todefine a processing volume, and generating an electric field with axialand radial components inside the processing volume by application of RFpower to the first electrode and DC power to the first ground plane.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1A (prior art) is a cross-sectional view of a substrate treatedaccording to a prior art process.

FIG. 1B (prior art) is a detail view of the substrate of FIG. 1A.

FIG. 2A is a schematic cross-sectional view of a plasma processingchamber in accordance with one embodiment of the present invention.

FIG. 2B is a schematic side view of the plasma processing chamber ofFIG. 2A.

FIG. 3 is a schematic side view of another embodiment of a plasmaprocessing chamber according to the present invention.

FIG. 4 a schematic side view of another embodiment of a plasmaprocessing chamber according to the present invention.

FIG. 5 is a schematic side view of another embodiment of a plasmaprocessing chamber according to the present invention.

FIG. 6 is a schematic side view of another embodiment of a plasmaprocessing chamber according to the present invention.

To facilitate understanding, identical reference numerals have beenused, wherever possible, to designate identical elements that are commonto the figures. It is also contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

The present invention generally provides methods and apparatus forcontrolling the spatial distribution of a plasma during processing of asubstrate in a plasma reactor having a plasma generator with parallelelectrodes.

FIG. 2A is a schematic cross-sectional view of one embodiment of aplasma enhanced chemical vapor deposition (PECVD) system 100. The PECVDsystem 100 generally comprises a chamber body 102 supporting a chamberlid 104 which may be attached to the chamber body 102 by one or morefasteners, such as screws, bolts, hinges, and the like. The chamber body102 comprises chamber sidewall 112 and a bottom wall 116 defining aprocessing volume 120 for containing a plasma 103 between a substratesupport 128 and a showerhead assembly 142. A controller 175 is coupledto the system 100 to provide process control, such as gas delivery andexhaust, transfer functions, among other functions.

The chamber lid 104 is coupled to a gas distribution system 108 fordelivering reactant and cleaning gases into the processing volume 120via the shower head assembly 142. The shower head assembly 142 includesa gas inlet passage 140 which delivers gas into the processing volume120 from one or more gas inlets 168, 163, and 169. A remote plasmasource (not shown) may be coupled between the processing volume 120 andthe gas inlets 168, 163, and 169. The PECVD system 100 may also includea liquid delivery source 150 and a gas source 172 configured to providea carrier gas and/or a precursor gas. A circumferential pumping channel125 formed in the sidewall 112 and coupled to a pumping system 164 isconfigured for exhausting gases from the processing volume 120 andcontrolling the pressure within the processing volume 120. A chamberliner 127, preferably made of ceramic or the like, may be disposed inthe processing volume 120 to protect the sidewall 112 from the corrosiveprocessing environment. A plurality of exhaust ports 131 may be formedon the chamber liner 127 to couple the processing volume 120 to thepumping channel 125.

A base plate 148 integrates the chamber lid 104, gas distribution system108 and shower head assembly 142. A cooling channel 147 is formed in thebase plate 148 to cool the base plate 148 during operation. A coolinginlet 145 delivers a coolant fluid, such as water or the like, into thecooling channel 147. The coolant fluid exits the cooling channel 147through a coolant outlet 149.

The substrate support 128 is configured for supporting and holding asubstrate 121 during processing. The substrate support 128 is adapted tomove vertically within the processing volume 120, and may additionallybe configured to rotate by a drive system coupled to a stem 122. Liftpins 161 may be included in the substrate support 128 to facilitatetransfer of substrates into and out of the processing volume 120. In oneembodiment, the substrate support 128 includes at least one electrode123 to which a voltage is applied to electrostatically secure thesubstrate 121 thereon. The electrode 123 is powered by a direct current(DC) power source 176 connected to the electrode 123. Although thesubstrate support 128 is depicted as a monopolar DC chuck, embodimentsdescribed herein may be used on any substrate support adapted tofunction as a ground plane in a plasma chamber and may additionally be abipolar chuck, a tripolar chuck, a DC chuck, an interdigitated chuck, azoned chuck, and the like.

The substrate support 128 may comprise heating elements 126, for exampleresistive heating elements, to heat the substrate 121 positioned thereonto a desired process temperature. The heating elements 126 may becoupled to an alternating current (AC) power supply (not shown)configured to provide a voltage, such as about 208 volts to the heatingelements 126.

A radio frequency (RF) power source 165 is coupled to the showerheadassembly 142 through an impedance matching circuit 173. The faceplate146 of the showerhead assembly 142 and the electrode 123, which may begrounded via an electronic filter, such as a capacitor 190, form acapacitive plasma generator. The RF source 165 provides RF energy to theshowerhead assembly 142 to facilitate generation of a capacitive plasmabetween the faceplate 146 of the showerhead assembly 142 and thesubstrate support 128. Thus, the electrode 123 provides both a groundpath for the RF source 165 and an electrical bias from DC power source176 to enable electrostatic clamping of the substrate 121.

The substrate support 128 generally comprises a body made of a ceramicmaterial, such as aluminum oxide (Al₂O₃), aluminum nitride (AlN),silicon dioxide (SiO₂), or other ceramic materials. In one embodiment,the body of the substrate support 128 is configured for use at atemperature in the range of about −20° C. to about 700° C. The electrode123 may be a mesh, such as an RF mesh, or a perforated sheet of materialmade of molybdenum (Mo), tungsten (W), or other material with asubstantially similar coefficient of expansion to that of the ceramicmaterial comprising the body of the substrate support 128. The electrode123 embedded in substrate support 128, together with faceplate 146 ofshowerhead assembly 142, cooperatively define processing volume 120.

The RF source 165 may comprise a high frequency radio frequency (HFRF)power source, for example a 13.56 MHz RF generator, and a low frequencyradio frequency (LFRF) power source, for example a 300 kHz RF generator.The LFRF power source provides both low frequency generation and fixedmatch elements. The HFRF power source is designed for use with a fixedmatch and regulates the power delivered to the load, eliminatingconcerns about forward and reflected power.

The electrode 123 is coupled to a conductive member 180. The conductivemember 180 may be a rod, a tube, wires, or the like, and be made of aconductive material, such as molybdenum (Mo), tungsten (W), or othermaterial with a substantially similar coefficient of expansion withother materials comprising the substrate support 128. The electrode 123functions as a return path for RF power and a biasing electrode toenable electrostatic chucking of the substrate. In order to provide anelectrical bias to the substrate 121, the electrode 123 is incommunication with a power supply system 182 that supplies a biasingvoltage to the electrode 123. The power supply system 182 includes DCpower source 176 to supply a DC signal to the electrode 123 and anelectronic filter 186 adapted to filter voltage fluctuations between DCpower source 176 and electrode 123. In one embodiment, DC power source176 is a 24 volt DC power supply and the electrical signal may provide apositive or negative bias.

DC power source 176 may be coupled to an amplifier 184 to amplify theelectrical signal from DC power source 176. Voltage fluctuations arefiltered by electronic filter 186 to prevent DC power source 176 andamplifier 184 from suffering voltage spikes. In one embodiment, filter186 may be an inductor 188 with capacitors 190 and 192 in parallel. Theamplified and filtered electrical signal is provided to the electrode123 and the substrate 121 to enable electrostatic clamping of thesubstrate 121. Capacitors 190 and 192 also allow electrode 123 tofunction as a ground member for RF power, wherein RF power is coupled toground by connectors 194 and 196. Capacitors 190 and 192 prevent DCpower from DC power source 176 from going to ground, while passing RFpower. In one embodiment, the capacitors 190 and 192 may each be 0.054micro Farad (μF) capacitors at 10-15 amps and about 2000 volts. In thismanner, the electrode 123 functions as a substrate biasing electrode anda return electrode for RF power.

As described above, the electrode 123 provides a bias from DC powersource 176 and functions as a ground path for RF energy from RF powersource 165. The capacitively coupled plasma 103 generated in theprocessing volume 120 may be tuned by the matching circuit 173 based onsignals from the controller 175. However, the configuration of theelectrode 123, in its function as a ground plane for RF energy, may notprovide an acceptable plasma discharge or spatial distribution. Forexample, the periphery of the substrate 121 may encounter onlyintermittent plasma discharge, which results in incomplete or reduceddeposition at the periphery. In another example in reference to FIGS. 1Aand 1B, the periphery of the plasma 103 may produce a region 15 alongthe periphery of the substrate, which may be an area where excessivedeposition and build-up of deposited material occurs on the substrate121.

In the embodiment illustrated by FIG. 2A, the electrode 123 may beshaped to counteract plasma edge effects described in connection withFIGS. 1A and 1B. Angling the periphery of the electrode 123, as shown inthis embodiment, results in generation of an electric field havingradial as well as axial components inside the processing volume 120. Thepotential difference between the electrode 123 and the face plate 146 isdifferent at different points on the electrode 123. These potentialdifferences result in electrostatic forces that push charged particlesfrom the face plate 146 to the electrode 123, the axial component of theelectric field, and closer to or further from the center of the chamber,the radial component of the electric field. Additionally, the electrode123 may be tuned by adjusting DC power to the electrode based on signalsfrom the controller 175. In this way, the ground plane for the plasmagenerator, exemplified in this embodiment by the electrode 123, istunable and allows for mitigation of plasma edge effects.

FIG. 2B is another schematic side view of the plasma processing chamberof FIG. 2A, showing the electrode 123 more distinctly within thesubstrate support 128. The electric field creates a plasma 103 bycapacitive coupling of a process gas provided to a processing volume 120through the face plate 146. In this embodiment, the electrode 123features a flat portion 204 and an angled portion 205. The flat portion204 of the electrode 123 comprises a first portion that defines a plane,and the angled portion 205 comprises a second portion that defines asurface. The substrate support 128 defines a second plane. In thisembodiment, the first plane defined by the flat portion 204 and thesecond plane defined by the substrate support 128 are substantiallyparallel, while the first plane intersects the surface defined by theangled portion 205. In this way, the electrode 123 exhibits athree-dimensional structure that results in an electric field withradial and axial components. The angled portion 205 of the electrode 123curves the electric field lines within the processing volume 120 in away that spreads plasma 103 to cover a substrate 121 disposed on thesubstrate support 128 more completely.

For embodiments featuring an electrode 123 with an angled edge, asillustrated by FIG. 2B, the angled portion 205, in cross-section, willform an angle with the flat portion 204 that is preferably between about90° and about 170°, such as about 1350. In the embodiment shown in FIG.2B, the angled portion 205 of the electrode 123 thus forms an obtuseangle with the flat portion 204, and is angled away from the surface ofthe substrate support 128. In other embodiments, the angled portion 205may be angled toward the surface of the substrate support 128, or may becurved toward or away from the surface of the substrate support 128. Insome embodiments, the edges of the electrode 123 may extend beyond theedges of a substrate disposed on the substrate support 128. In otherembodiments, the edges of a substrate may extend beyond the edges of thesubstrate support 128 and the electrode 123. In still other embodiments,the electrode 123 is embedded in the substrate support 128 at a depthsuch that the distance between the flat portion 204 of the electrode 123and the surface of the substrate support 128 is between about 5 and 10mm. In some embodiments, the angled portion 205 may be configured suchthat the end of the angled portion 205 furthest from the flat portion204 is between about 25% and about 50% further from the surface of thesubstrate support 128 than the flat portion 204. In other embodiments,the portion of the substrate support 128 extending beyond the edge ofthe electrode 123 may be between about 1 mm and about 3 mm in width.

In other embodiments, portion 205 is an edge portion and portion 204 isa central portion of electrode 123. Portion 205 may be raised or loweredrelative to portion 204 such that portions 204 and 205 define planeswhich are substantially parallel, but portion 205 may be closer to, orfurther from, the surface of substrate support 128. In some embodiments,portion 205 may be displaced from portion 204 between about 0.5 mm andabout 2 mm. There may be a sloped portion joining portions 204 and 205,which may form angles with portions 204 and 205, or may form curvedjoints with portion 204 and 205.

Additionally, portion 205, whether angled or not with respect to portion204, may have a thickness that is more or less than portion 204. Thethickness of portion 205 may deviate from that of portion 204 by up toabout 0.5 mm, such that portion 205 is up to 0.5 mm thinner than portion204, or portion 205 is up to 0.5 mm thicker than portion 204. Thethickness of either portions 204 or 205 may also be tapered. Forexample, portion 205 may be up to about 3 mm. thick where it joinsportion 204, and may taper to a thickness of 0.5 mm or less at its edge.Portion 205 may likewise be fitted with a shaped edge, such as a beadwith shaped cross-section, such as a circular bead attached to the edgeof portion 205. The bead may have any advantageous shape in crosssection, such as triangular, square, or trapezoidal.

FIG. 3 is a schematic side-view of a plasma processing chamber accordingto another embodiment. In this embodiment, chamber 300 features a zonedshowerhead assembly 360. The face plate 146 of the showerhead assembly360 is separated into discrete conductive zones by electrical isolators370. In one embodiment, RF power is applied to each zone separately byindependent RF sources 165 and 330 through independent matching networks173 and 340, respectively, all under control of a controller 175. Inanother embodiment, a single RF source provides power to each zone, orto all zones collectively. A voltage bias is applied to the electrode123, as described above, with the DC biasing source collectivelyrepresented by element 350, which may include filters, such as filter186, and amplifiers, such as amplifier 184, as described above, and iscoupled to the electrode 123 by a connector. The zoned showerheadassembly 360 is coupled to the independent RF sources 165 and 330, whichallows different power levels to be applied to the zones through theindependent impedance matching networks 173 and 340 to tune the electricfield inside the processing volume 120 to control the spatialdistribution of plasma 103.

FIG. 4 is a schematic side-view of a plasma processing chamber accordingto another embodiment of the invention. In this embodiment, a chamber400 utilizes an electrode 410 embedded in the chamber sidewall 112. Thechamber wall electrode 410 is made of a suitable conductive material,such as aluminum, and is isolated from the sidewall 112 by an isolator320 and from chamber lid 104 by an isolator 105. Each isolator may bemade of any suitable insulating material, but is preferably made of amaterial with thermal characteristics similar to the materials of thechamber wall. One such material is ceramic. In this embodiment, avoltage bias is applied to the electrode 123 as above, with DC source,amplifiers, and filters, as described above in reference to FIG. 2A,collectively represented by DC element 350, which is coupled to theelectrode 123 by a connector. A similar bias generator 420 may becoupled to the chamber wall electrode 410. The controller 175 may beadapted to control application of RF power to the face plate 146, biaspower to the electrode 123, and bias power to the chamber wall electrode410 to ensure adequate coverage of a substrate 121 by plasma 103.

FIG. 5 is a schematic side-view of a plasma processing chamber 500according to another embodiment of the invention. In this embodiment,the chamber wall electrode 410 is not isolated from the sidewall 112, soplasma 103 may couple directly with the chamber wall, as well as withthe electrode 123, such that the chamber wall electrode 410, thesidewall 112, and the electrode 123 collectively serve as ground planes.DC bias applied to the chamber wall electrode 410 is thus applied to theentire chamber wall, causing plasma 103 to spread toward the peripheryof the processing volume 120 and cover the substrate 121. An insulator520 is provided to prevent electric discharges from the sidewall 112,and an isolator 105 isolates a lid assembly 148 from the rest of thechamber.

FIG. 6 is a schematic side-view of a plasma processing chamber 600according to another embodiment of the invention. In this embodiment,two electrodes 623A and 623B are embedded within the substrate support128. As before, each electrode is configured to serve as a ground planefor RF power, while applying DC voltage bias to clamp a substrate 121 inplace. Each electrode is separately biased by DC bias generators 610 and620, respectively. As before, each DC bias generator comprises a DCsource with amplifiers and filters as necessary. The ability to tune theground planes independently provides the capability to shape theelectric field inside the processing volume 120 to control the spatialdistribution of plasma 103 to minimize or eliminate plasma edge effects.

The embodiments described above are examples incorporating elements ofthe invention in demonstrable ways. Any combination of the aboveelements may be used to tune and shape plasma 103 inside the processingvolume 120 for complete coverage of a substrate 121 without edgeeffects. Any combination of multiple electrodes, shaped or unshapedground members, bias generators, isolators, and the like, may be used.For example, multiple shaped ground members, or a single shaped groundmember with a sidewall electrode, may be used. A zoned showerheadelectrode may also be used with one or more shaped ground members, andwith one or more sidewall electrodes.

In operation, a substrate is disposed on a substrate support inside aplasma processing chamber according to any of the embodiments describedabove. Process gases are supplied to the processing chamber through ashowerhead assembly, which comprises a first electrode. RF power isapplied to the first electrode by coupling an RF generator through animpedance matching network to the first electrode. The RF generator maygenerate high-frequency power, such as about 13.56 MHz, or low-frequencypower, such as about 300 kHz. Application of RF power to the firstelectrode creates an oscillating electric field inside the processingchamber, and ionizes the process gases into a plasma.

The substrate is disposed on a substrate support with a ground memberembedded therein. The ground member serves as an electrode for couplingDC power to the substrate support, and together with the firstelectrode, defines a processing volume in the processing chamber. DCpower is coupled to the electrode using connectors that run through thesubstrate support. DC power is applied to the electrode, creating avoltage bias in the electrode that results in the substrate beingclamped securely to the substrate support. An electronic filter may beprovided between the DC power source and the electrode disposed in thesubstrate support so that the electrode may serve as a path to groundfor the RF power, while applying a DC voltage bias to the substrate. Inthis way, the electrode in the substrate support may serve as a groundmember for the RF power. A controller may be used to adjust the powerdelivered to the plasma by tuning the impedance of the match network.The controller may also be used to adjust the power output of the DCsource to tune the electric field inside the processing chamber. In thisway, an electric field having radial as well as axial components isgenerated, allowing adjustment of the spatial distribution of the plasmatoward or away from the center of the chamber for full coverage of thesubstrate.

In this embodiment, the ground member is shaped to produce the desiredfield properties. For example, the ground member may feature a firstportion substantially parallel to the surface of the substrate support,and a second portion tapered from the first portion. The first portiondefines a plane, and the second portion defines a surface thatintersects the plane. A shaped ground member may thus define a pluralityof intersecting surfaces.

In an alternative embodiment, multiple ground members may be provided.For example, a second ground member having a different shape from thefirst ground member may be embedded inside the substrate support. Acontroller may separately tune the bias applied to each ground member tocreate the desired spatial distribution of the plasma.

In another embodiment, a zoned showerhead electrode may be used togenerate a tunable electric field. RF power may be providedindependently through different match networks to the different zones. Acontroller may be used to tune the power provided to each zone byadjusting the impedance of the match networks. A DC voltage bias isapplied to an electrode embedded in the substrate support to clamp thesubstrate and provide a path to ground for the RF power, as discussedabove. In this embodiment, tuning the power delivery to the differentzones of the showerhead electrode results in an electric field havingradial as well as axial components, and allows control of the spatialdistribution of the plasma.

In an alternative embodiment, the electric field and plasma may beradially adjusted by providing an electrode in the sidewall of theprocessing chamber. In some embodiments, the chamber wall itself may beused as the electrode. The electrode may be grounded or biased inaddition to the electrode embedded in the substrate support. Acontroller may be used to independently adjust the bias of the substratesupport electrode, the sidewall electrode, and the power delivered tothe showerhead electrode to adjust the spatial distribution of theplasma.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An apparatus for processing a substrate, comprising: a substratesupport; one or more electrodes coupled to the substrate support; ashowerhead assembly having a face plate opposing the substrate support;and one or more ground elements spaced radially away from the substratesupport, wherein the substrate support and the face plate cooperativelydefine a processing volume and the one or more electrodes are adapted togenerate a tunable electric field inside the processing volume havingaxial and radial components.
 2. The apparatus of claim 1, wherein theone or more electrodes is disposed within the substrate support.
 3. Theapparatus of claim 1, wherein a portion of at least one of the one ormore electrodes is angled.
 4. The apparatus of claim 1, furthercomprising one or more tunable circuits coupled to at least one of theone or more ground planes.
 5. The apparatus of claim 4, furthercomprising one or more tunable circuits coupled to at least one of theone or more electrodes.
 6. The apparatus of claim 1, further comprisinga DC power source coupled to at least one of the one or more electrodes.7. The apparatus of claim 1, wherein the face plate is divided intozones separated by one or more isolators.
 8. The apparatus of claim 7,further comprising isolators disposed between the one or more groundplanes.
 9. The apparatus of claim 1, wherein at least one of the one ormore ground planes is an RF mesh.
 10. The apparatus of claim 1, whereinat least one of the one or more ground planes is the chamber bottom. 11.An apparatus for supporting a substrate in a processing chamber,comprising: a support surface; a thermal control element disposed withinthe support surface; an electrode disposed within the support surface,wherein the electrode has a first portion defining a first plane and asecond portion defining an angled surface, and the angled surfaceintersects the first plane; and a tuner coupled to the electrode. 12.The apparatus of claim 11, further comprising an electronic filtercoupled to the electrode.
 13. The apparatus of claim 11, wherein thesupport surface defines a second plane, and the first plane issubstantially parallel to the second plane.
 14. The apparatus of claim11, wherein the electrode is an RF mesh.
 15. A method of controlling thespatial distribution of a capacitively coupled plasma, comprising:positioning a first electrode inside a processing chamber; positioning afirst ground plane inside the processing chamber and facing the firstelectrode to define a processing volume; and generating an electricfield with axial and radial components inside the processing volume byapplication of RF power to the first electrode and DC power to the firstground plane.
 16. The method of claim 15, further comprising positioninga second ground plane inside the processing chamber.
 17. The method ofclaim 15, further comprising using the first ground plane to provide apath to ground for the RF power and to apply a voltage bias inside theprocessing volume.
 18. The method of claim 16, further comprising tuningat least one of the first and the second ground planes.
 19. The methodof claim 16, wherein the second ground plane has a different shape fromthe first ground plane.
 20. The method of claim 15, wherein the groundplane has a shape defined by a plurality of intersecting surfaces.